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US-12620624-B2 - Non-aqueous electrolytic solution for lithium secondary battery and lithium secondary battery comprising same

US12620624B2US 12620624 B2US12620624 B2US 12620624B2US-12620624-B2

Abstract

An electrolyte for a lithium secondary battery including a wettability-improving additive having a trifluoromethylsulfonyl group. The electrolyte has reduced surface tension to improve the wettability of an electrode assembly with the electrolyte. Therefore, it is possible to ensure high electrolyte wettability even when the electrolyte includes a high-boiling point solvent or a high concentration of lithium salt.

Inventors

  • Jeong-Beom Lee
  • Ye-Eun Kim
  • Seok-Koo Kim
  • Je-Young Kim

Assignees

  • LG ENERGY SOLUTION, LTD.

Dates

Publication Date
20260505
Application Date
20211130
Priority Date
20201130

Claims (5)

  1. 1 . A non-aqueous electrolyte for a lithium-ion secondary battery, comprising a lithium salt, an organic solvent and a wettability-improving additive, wherein the wettability-improving additive consists of 1H,1H,5H-Octafluoropentyl trifluoromethanesulfonate, and is included in an amount of 0.05-3 wt % based on a total weight of the non-aqueous electrolyte, the organic solvent comprises nitrile-based solvent in an amount of 95 wt % or more based on a total amount of the organic solvent, and the nitrile-based solvent comprises succinonitrile.
  2. 2 . The non-aqueous electrolyte for a lithium ion secondary battery according to claim 1 , wherein the lithium salt comprises a Li + as a cation, and at least one anion selected from the group consisting of F − , Cl − , Br − , I − , NO 3 − , N(CN) 2 − , BF 4 − , ClO 4 − , AlO 4 − , AlCl 4 − , PF 6 − , SbF 6 − , AsF 6 − , B 10 Cl 10 − , BF 2 C 2 O 4 − , BC 4 O 8 − , PF 4 C 2 O 4 − , PF 2 C 4 O 8 − , (CF 3 ) 2 PF 4 − , (CF 3 ) 3 PF 3 − , (CF 3 ) 4 PF 2 − , (CF 3 ) 5 PF − , (CF 3 ) 6 P − , CF 3 SO 3 − , C 4 F 9 SO 3 − , CF 3 CF 2 SO 3 − , (CF 3 SO 2 ) 2 N − , (FSO 2 ) 2 N − , CF 3 CF 2 (CF 3 ) 2 CO − , (CF 3 SO 2 ) 2 CH − , CH 3 SO 3 − , CF 3 (CF 2 ) 7 SO 3 − , CF 3 CO 2 − , CH 3 CO 2 − , PO 2 F 2 − , SCN − and (CF 3 CF 2 SO 2 ) 2 N − .
  3. 3 . The non-aqueous electrolyte for a lithium-ion secondary battery according to claim 1 , wherein the nitrile-based organic solvent further comprises adiponitrile, acetonitrile, propionitrile, butyronitrile, glutaronitrile, pimelonitrile, suberonitrile, valeronitrile, caprylonitrile, heptane nitrile, cyclopentane carbonitrile, cyclohexane carbonitrile, 2-fluorobenzonitrile, 4-fluorobenzonitrile, difluorobenzonitrile, trifluorobenzonitrile, phenylacetonitrile, 2-fluorophenyl acetonitrile, 4-fluorophenylacetonitrile, or a combination thereof.
  4. 4 . The non-aqueous electrolyte for a lithium-ion secondary battery according to claim 1 , wherein a concentration of the lithium salt is 1.5 M or more.
  5. 5 . A lithium secondary battery comprising a positive electrode, a negative electrode, a separator and the non-aqueous electrolyte for a lithium-ion secondary battery according to claim 1 .

Description

CROSS-REFERENCE TO RELATED APPLICATIONS The present application is a US national phase of international Application No. PCT/KR2021/017918 filed on Nov. 30, 2021, and claims priority to Korean Patent Application No. 10-2020-0165008 filed on Nov. 30, 2020, the contents of which are incorporated for all purposes as if fully set forth herein. TECHNICAL FIELD The present disclosure relates to an electrolyte for a lithium secondary battery and a lithium secondary battery including the same. BACKGROUND As information society and personal IT devices and computer networks have been developed, and the overall social dependence on electric energy has increased, there is a need for developing technologies for storing and utilizing electric energy efficiently. Among the technologies developed for the above-mentioned purpose, the most suitable technology for various uses is a secondary battery-based technology. In the case of a secondary battery, it can be downsized to such a degree that it may be applied to personal IT devices, and the like, and can also be applied to electric vehicles, electric power storage systems, and the like. Therefore, such secondary batteries have been spotlighted. Among the secondary battery technologies, lithium-ion batteries which are battery systems having, theoretically, the highest energy density have been given a lot of attention and have been applied to various devices. A lithium-ion battery does not apply lithium metal directly to an electrode, but includes a positive electrode including a lithium-containing transition metal oxide, a negative electrode including a carbonaceous material, such as graphite, capable of storing lithium, an electrolyte functioning as a medium for conducting lithium ions, and a separator. Among such components, the electrolyte has been known to affect the stability and safety of a battery significantly, and has been studied intensively. The electrolyte for a lithium secondary battery includes a lithium salt, an organic solvent for dissolving the lithium salt, and functional additives, and the like. To improve the electrochemical properties of a battery, it is important to select such ingredients suitably. Typical lithium salts that are currently used include LiPF6, LiBF4, LiFSI (lithium fluorosulfonyl imide, LiN(SO2F)2), LiTFSI (lithium (bis)trifluoromethanesulfonyl imide, LiN(SO2CF3)2), LiBOB (lithium bis(oxalate) borate, LiB(C2O4)2), and the like. In addition, an ester-based organic solvent or an ether-based organic solvent is used as the organic solvent. Recently, the use of an electrolyte containing a high concentration of lithium salt or a high-boiling point solvent having a boiling point of 150° C. or higher has been suggested to further improve the performance, particularly, heat resistance or electrochemical stability, of a lithium secondary battery. However, such an electrolyte material shows lower affinity to an electrode and lower affinity to a separator and has higher surface tension, as compared to a carbonate-based electrolyte mixed with 1.0-1.2 M of lithium salt, and thus is problematic in that it shows significantly low wettability to a polyolefin-based separator and an electrode using PVDF as a binder, that are generally used in lithium secondary batteries. When the electrode/separator wettability is significantly low as mentioned above, activation processing time increases during a process for manufacturing a battery, and a high-temperature aging step is used to make the overall process complicated, resulting in an increase in the cost of the battery. In addition, the life characteristics and high-rate charging and output characteristics of a battery are affected adversely, which functions as an obstacle in applying such a novel electrolyte to commercialized batteries. Thus, there is a need for developing a liquid electrolyte that does not degrade the wettability of an electrode assembly with an electrolyte when using a high concentration of lithium salt or an organic solvent, such as a high-boiling point solvent, as an ingredient of the electrolyte. SUMMARY The present disclosure is designed to solve the problems of the related art, and is directed to providing a liquid electrolyte capable of improving electrode wettability. The present disclosure is also directed to providing a lithium-ion secondary battery including the liquid electrolyte. These and other objectives and advantages of the present disclosure may be understood from the following detailed description. Also, it will be easily understood that the objectives and advantages of the present disclosure may be realized by the embodiments of the appended claims and combinations thereof, but are not limited thereto. According to a first embodiment of the present disclosure, there is provided a non-aqueous electrolyte for a secondary battery, including a lithium salt, an organic solvent and a wettability-improving additive, wherein the wettability-improving additive has a trifluoromethyl